The present invention is concerned with lap siding panels of the type wherein elongate siding panels of sheet metal or vinyl are formed with mating, interlocking means along their opposed longitudinal edges for interlocked installation on a building wall in imitation of conventional wooden lap siding. Panels of this type have long been known in the art. Because the panels function solely to provide a weatherproof exterior sheathing of the building and do not provide any structural support, they are conventionally made of relatively thin material which does not provide any substantial heat insulation to the building. Accordingly, it has been proposed in the prior art to back such panels with boardlike members of heat insulating material, such as expanded polystyrene foam, for example. See U.S. Pat. Nos. 3,826,054 and 4,081,939, for example.
While improvement in insulating qualities of the siding panel is thus obtained, the configuration of the metal (or vinyl) outer panels, particularly the interlocking edges, and the clearances required to enable adjacent panels to be interlocked with each other during installation, find most prior art composite panels having recesses or voids provided in the boardlike insulating member which leave internal chambers in the finally assembled and installed panels which permit thermal losses due to air infiltration, tend to collect moisture, provide nesting places for insects, or result in gaps or regions of substantially reduced thickness in the insulating material. Overall, such boardlike members have a thickness ranging between 3/8" to 1/2" and therefore provide little or no structural support and little insulation value to the siding panels.
The present invention is especially directed to a composite panel of the foregoing type in which a boardlike member of insulating material is bonded at the factory to the metal or vinyl outer panel and is formed with a cross-sectional configuration such that the metal and its attached insulating board are both firmly and permanently anchored to the building frame during installation, in which the insulating material does not interfere with the interlocking of a subsequent panel, and in which a substantially void-free insulating layer, which may be of any desired thickness to eliminate the need for sheathing in new construction and to afford substantially greater "R" values, is achieved behind the metal panels in the completed installation.